1. Field of the Invention
The present invention relates to a supercooling apparatus and a control method thereof. The present invention relates to a supercooling apparatus, which can control supercooling temperatures differently according to a kind of beverage when storing various beverages in a supercooled state, and a control method thereof.
2. Description of the Related Art
Generally, a refrigerator includes a refrigerating compartment and a freezing compartment, and provides the simple function of storing various foods at low temperatures. Recently, there has been proposed a new type of refrigerator, which can satisfy not only the function of storing various foods at low temperatures, but also the function of producing supercooled beverages, which can be used for making, for example, a slush beverage, using a supercooling apparatus.
At this time, the slush beverage has a coexistence state wherein a solid phase and a liquid phase coexist. The beverage generally changes in phase from liquid to solid below a freezing point at a pressure of 1 atm, but in some cases, it is in a supercooled state not in the solid phase. Such a state wherein a liquid is in a supercooled state not in the solid phase below the freezing point is thermodynamically called a meta-stable state. When the beverage is in the meta-stable state, the beverage is in neither an equilibrium state nor a completely unstable state. Thus, if there is external disturbance, the beverage instantaneously changes in phase from the supercooled state to the solid phase. In other words, when the supercooled beverage is poured to a cold cup, or subjected to impact or vibration, it becomes the slush beverage wherein the phase thereof is not in a completely frozen or melted state. At this time, since a temperature range for maintaining the beverages in the supercooled state is determined by contents of the beverages and other factors, the temperature ranges for maintaining the beverages are generally different from one another according to the kind of beverage.
Various types of supercooling apparatus are well known in the art. For example, Japanese Laid-open Patent Publication No. 2003-214753 discloses a refrigerating apparatus for supercooling beverages. The refrigerating apparatus of the publication includes a chilled air supplying duct and chilled air suctioning duct respectively positioned along opposite sides of a storage compartment in a body, a connection duct positioned along an upper side of the storage compartment to connect the chilled air supplying duct to the chilled air suctioning duct, a fan installed to the connection duct, a chilled air outlet port positioned in the chilled air supplying duct, and a chilled air suction port positioned in the chilled air suctioning duct to make the beverages in a supercooled state within the storage compartment.
However, disregarding the fact that the beverages are frozen from the supercooled state at different freezing points, the conventional refrigerating apparatus stores all the beverages at the same temperature in the storage compartment, causing a problem in that some beverages are frozen earlier from the supercooled state than others. In other words, when a certain beverage having a higher freezing point than that of other beverages is stored at a lower temperature than its freezing point within the storage compartment, the beverage is frozen earlier from the supercooled state than others.
In addition, disregarding the fact that a critical supercooling degree (difference between a storing temperature and a freezing point) of a certain beverage changes according to the storing temperature and the freezing point, and that a ratio of supercooled grains (hereinafter referred to as a “slush level”) in a slush beverage also changes according to the critical supercooling degree, the conventional refrigerating apparatus stores all the beverages at the same temperature, causing a problem in that the slush level is different according to kinds of beverage.